Apparatus for producing minute orifices



March 1, 1949. J. R. BOWMAN EIAL 2,453,239

APPARATUS FOR PRODUCING MINUTE ORIFICES Filed Feb. 19, 1945 JOHN R.BOWMHN roman" 2r VLRSAW Fatented Mar. 1, 1949 APPARATUS FOR raonucmcMINUTE cannons I John R. Bowman, Pittsburgh, and Forest F. Versaw, PennTownship, Allegheny County, Pa., assignors to Gulf Research &Development Company, Pittsburgh, Pa., a corporation of DelawareApplication February 19, 1945. Serial No. 578,786

3 Claims. i

This invention relates to an apparatus for reducing orifices to minutesize and, more specificaliv, for producing minute orifices of asubmicroscopic diameter for use in mass spectrometers.

Flow restricting devices have been used in mass spectrometers andsimilar equipment wherein a gas sample is admitted to an ionizationchamber and is subjected to a stream of accelerated electrons. Thesedevices should strongly impede the flow and for this purpose capillarytubes have been used. It is desirable that the gas be admitted through aplate or disc, but it has not been previously possible to provide aplate or disc with a hole of such extremely small diameter. Themolecules of entering as should radiate symmetrically from theintroduction point and consequently the orifice should be round.

It is accordingly a primary object of this invention to provideapparatus for producing a round minute orifice in a perforated plate ordisc.

Other and further objects of the invention will be apparent from thefollowing description of the invention whereby it will be seen that theobjects are attained.

In general, the invention relates to an apparatus for producing a minuteorifice in a plate. More specifically, the apparatus comprises an anvilhaving a fiat polished surface of at least as great a diameter as thatof the plate which is to be provided with a minute orifice. A collarsurrounding the anvil and extending beyond the facethereof retains andlocates the plate. There is also provided a die which is received withinand guided by the collar and'which has a surface accurately flat andpolished. The die is so shaped that it transmits impact forces to theplate with radial symmetry.

In the accompanying drawing:

Fig. 1 is a side view of an apparatus for making impacts on a discpositioned thereon;

Fig. 2 is a plan view of the apparatus;

Fig. 3 is a sectional view along line 33 of Fig. 1;

Fig. 4 is a sectional view along line 4-4 of Fig. 1;

Fig. 5 is a magnified view taken through the center of a drilled blank;and

Fig. 6 is a similarly magnified view of the completed orifice.

Parallel guide rods 10 and II extend vertically from a base Bend aresecured at their upper. threaded ends by a cross member l3 which isretained and secured by nuts l4 and IS. A weight I6 is mounted on therods which guide it in vertical movement, and the weight carries aprojectface such as a plane piece of quartz. It is sub-' jected toannealing by heating to a dull red heat I 2 ing hammer element H fordelivering blows to an underlying anvil and die assembly. The anvil 18comprises a flanged base l9 with a central 1 upstanding portion 20 whichhasa flat and polished upper surface. Bolts or fillister screws 2!extend into arcuate cutout portions 22 of the flange l9 and. secure theanvil to the case n through the medium of a collar 23 which iscount-ersunk to receive the heads of the bolts or screws. In this mannerthe anvil is anchored and is prevented elther from rotation or tilting.

A retaining ring 24 is adapted to slip-overthe end of the uprightportion 20, to-retain and align a disc blank 25 and a superimposed die28 for receiving impacts from the hammer member l1.

The top surface of the die 26 is rounded so that blows which aredelivered to it will be transmitted symmetrically to the disc blank. Itwill be understood, however, that the die may have a conical uppersurface, or may be of any other geometrical shape which willcause theforces of impact to be distributed uniformly over the area of theunderlying disc. The lower surface of the die in contact with the discis accurately fiat and polished.

In Figs. 5 and 6 are shown magnified views of the disc 25 wherein it isshown how the orifice 28 changes under the repeated impacts from thedrilled hole shown in Fig. 5 to the Orifice of Fig. 6 upon successiveimpacts.

The invention depends upon the principle of isotropic flow of thematerial under impact and the capability of the material to set aftereach impact. Annealed fine gold has such an isotropic fiow and a goldplate or disc in the center of which a hole has been made as by drillingmay be subjected to successive impacts such that the hole will be madesmaller without distorting its initial round shape.

In one embodiment of the invention, therefore. a fine gold disc is firstrolled to a thickness of 0.010 inch and a diameter of 1.0 cm. The discis made very smooth and fiat and a hole is drilled through its center.The hole initially should be as small as practicable, for-which purposean 0.0135 .inch drill may be used, although it is preferable to use aneven finer drill, such as an 0.00185. inch drill of the kind employed inmaking injection nozzles for Diesel engines. The disc is carefullycleaned and placed on a flat surin a. muiile furnace and then allowed tocool slowly with the furnace. Desirable results may The annealed discblank is then transferred to the accurately fiat surface of thesupporting portion 20 of the anvil and the annular collar 24 is slippedinto position to surround it and retain the die 28. The plane surfacesof the anvil and die between which the disc is received are highlypolished and great care must be observed in keeping them cleanthroughout the operation of reducing the disc, for as the holeapproaches submicroscopic size even oil is difiicult or impossible toremove from it.

The reduction in size of the orifice can be followed by microscopicexamination for the first few blows that are delivered by the fallingweight l6, but as the hole becomes progressively smaller its size can nolonger be determined by visual in= spection, and therefore must beascertained by test. In accordance with our invention the flow of air orgas at-a determined rate through the orifice is taken as a measure ofits useful size. Our invention accomplishes this by subjecting one sideof the orifice to reduced pressure of about 0.5 mm. of mercury, whileits other side is exposed to atmosphere (760 mm. of mercury) at about 70F. Under such standardized conditions the orifice will be found ofproper size for use in mass spectrometers and other apparatus providinggaseous ion sources when air or gas will pass through it at the rate of0.1 to 0.01 ml. per minute measured at atmospheric pressure.

The exact cross-sectional shape of the completed orifice is unknown, butit probably approxe imates that of a singie-sheeted hyperboloid ofrevolution, as shown in Fig. 6.

, The flow of material of the blank takes place outwardly as well asinwardly, but is so exceedingly slight that it is not affected by theretaining ring 24. The fiow is inward in the neigh borhood of thecentral hole, and decreasingly so out to about half the radius of thedisc. Outside of this region the flow is outward, causing the edgesurface to become slightly toroidal rather than cylindrical as it wasoriginally. In practice the increase in diameter of the disc is notmeasurable.

While the above description of the invention has emphasized thepreparation of a minute orifice for a mass spectrometer, the minuteorifices of our invention have other uses in some of which the orificeneed not be so small nor so perfectly round. For other purposes, othermaterials than gold which are capable of substantially isotropic fiowmay be used, such as, for example, alloys of gold such as goldplatinum,tin. aluminum, silver, copper, and plastics. For purposes of obtamin asomewhat symmetrical orifice, the metals mentioned should be annealed.

a erable that the original hole be drilled in the exact center of acircular disc. If a plate other than a disc is used, impact should beupon a surface centered about the hole. Further, if the impact is notupon the whole area of the plate, it should at least be on an areacovering the hole and many times greater than the crosssectional area ofthe hole to distinguish clearly from the method of making larger holessmaller, used by jewelers, in which the side walls of a hole are simplybroken down by the impact of a die on the side walls of a hole, or frompeening operations in general.

While the invention is preferably directed to the making of a minuteorifice in a plate or prefr ly a disc, the making of minute orifices inblanks of other shapes is contemplated, such as the making of smallorifices for use as spinnerets in the manufacture of artificial fibers.The spinneret may be a disc ora thimble. case of a thimble or othersimilar shape, the impact should take place against a surface conformingin shape. 'Thus, the term "plate" as used in the claims is intended toinclude a fiat piece of material including discs, as well as variousshapes which may be formed from a plate.

From the foregoing it will be understood that our invention provides anapparatus for producing minute orifices, of a size smaller than can bedrilled, by the application of impact applied to the surface of apierced plate having suitable fiow characteristics.

What we claim is:

1. Apparatus for producing a minute orifice in a plate which ispreliminarily formed with a small opening, comprising an anvil having anenlarged base and a central upstanding portion the upper face of whichis flat and polished, a collar mounted on the central upstandingportion, fastening means extending through the collar and through cutoutportions of the base to anchor the anvil and prevent it from eitherrotating or tilting, a ring closely fitting the upstanding portion andslidable thereon to rest on said collar and to project above the upperface of said upstanding portion, a die retained within said ring fordelivering impacts to a perforated plate positioned on the polished faceof the anvil, said die havinga fiat polished under surfaceand' aprotuberant upper surface of geometrically symmetrical shape wherebyimpact forces are transmitted to the plate with radial symmetry in thearea surrounding the perforation therein. I

2. Apparatus for reducing an orifice in a plate to minute size,comprising an anvil having an enlarged base and a central upstandingportion the upper face of which is fiat and polished, a

collar mounted on the central upstanding por-' tion, fastening meansextending through the collar and through cutout portions of the baseWhile the preferable operation of the appa -fratus of our invention hasbeen described as sue:

cessive impacts, substantial reduction in the size, of an orifice maytake place with a single impact.

However, it is preferable that the impacts be repeated and that they bemade with a comparato anchor'the anvil and prevent it from eitherrotating or tilting, a ring closely fitting the upstanding portion andslidable thereon to rest on said collar and to project above the upperface of said upstanding portion, a die retained within said ring fordelivering impacts to a perfo-a rated plate positioned on the polishedface of the anvil, said die having a fiat polished under surface and aprotuberant upper surface of conl-' cal shape whereby impact forces aretransmitted to the plate with radial symmetry as the perforation thereinis reduced to minute size.

3. Apparatusfor producing a minute orifice in In the a perforated plate,comprising an anvil having an enlarged base and a central upstandingportion the upper face of which is hat and polished, a collar mounted onthe central upstanding portion, fastening means extending through thecollar and through cutout portions of the base to anchor the anvil andprevent it from either rotating or tilting, a ring closely fitting theupstanding portion and siidable thereon to rest on said collar and toproject above the upper face of said upstanding portion, a die retainedwithin said ring for delivering impacts to a perforated plate positionedon the polished face of the anvil, said die having a flat polished undersurface and a protuberant upper surface of a spherical shape wherebyimpact forces are transmitted to the plate with radial symmetry in thearea surrounding the perforation therein.

JOHN R. BOWMAN.

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' REFERENCES CITED The following references are of record in the file ofthis patent:

